Telephone system



Jan. 9, 1934. R. F. STEHLIK 1,942,671

TELEPHONE SYSTEM Filed Sept. 4, 1931 Inuen1mr Hudulph Frank E'Z'Z-zlik Patented Jan. 9, 1934 UNITED STATES TELEPHONE SYSTEM Rudolph Frank Stehlik, Chicago, Ill., assignor to Associated Telephone and Telegraph Company, Chicago, 111., a corporation of Delaware Application September4, 1931, Serial No. 561,212,

and in Great Britain September 11, 1930 9 Claims. (Cl. 179-27) I The present invention relates to telephone systems and is more particularly concerned with arrangements for setting up calls between subscribers at a public exchange and subscribers in a private oflice or the like. The object of the invention is to provide a simple and cheap construction for efiecting the above operations and this is achieved according to the invention by arranging that the lines between the public exchange and the private office are adapted to be connected to any one of a plurality of local subscribers lines by the operation of a single key.

The invention will be better understood from the following description of one method of carthe accompanying drawing which shows the circuit' arrangement of a manual board for extending connections between subscribers at the local and main exchanges.

The lines extending to the public exchange are indicated by L1, L2 and L3. The line L3 has associated with it at its incoming end a drop indicator D3, a night alarm key NK3, a relay A3, a retard R3 and a lamp LAB, the equipment for the other two lines being similar. In addition to this apparatus a number of three-way switching keys are provided each corresponding to a local line having the privilege of main exchange connections. The switching key K1 is shown with connections extending to the instrument set OS and the other switching keys would be provided with similar connections. The equipment described is mounted on a board which is atttended to by one of the local subscribers, for example, the subscriber at the instrument set OS. To enable the manual board to be used in conjunction with a private automatic exchange, the operators instrument set and also the sets of the other subscribers connected to the manual board are of the type provided with two buttons for connecting the speaking and dialling instruments to either of two separate lines, a set of this type is shown in United States application No. 400,402 filed 17th October, 1929.

When an incoming call is extended over line L3, ringing current is transmitted through the winding of the indicator D3 which is thereby energized to allow the indicating flap to drop and attract the attention of the operator. The operator on perceiving that the line L3 is calling will operate the key K1, so as to actuate the upper set of springs, whereupon the talking conductors extending from her instrument set are connected to the trunk line. At the same time she presses button M of her instrument se rying it into efiect taken in conjunction with thereby connecting her hand-set across the trunk lines and tripping the ringing current; this circuit may be traced over the conductors shown in thick lines. Talking current is now fed from the public exchange and the operator ascertains the requirements of the calling party.

If the calling party wishes to be connected to a subscriber in the private office the operator presses button L on her instrument set, by this operation the springs operated by button M are restored to normal with the exception of springs H which maintain a loop across the trunk line to hold the connection at the public exchange. The operators set is now connected to the line OAL extending to the private automatic exchange and the operator by dialling can select the line of the wanted subscriber. The bell of the wanted subscriber is rung and when he replies the. operator offers him the call incoming from the public exchange. If the wanted subscriber de- 7 cides to accept this call he presses button M of his instrument set, and the operator operates the switching key corresponding to the wanted subscriber to actuate its upper set of springs and thereby connects the line of the wanted subscriber to the line L3.

It will be noted that relay A3 is included in the trunk line so that this relay operates, at its lower outer contact it completes a circuit for the busy lamp LA3 which thereupon glows continuously as long as the trunk line is in use. At its lower inner contact, relay A3 connects the retard R3 across the winding of indicator D3 so as to prevent the indicator operating while the line is in use.

If the incoming call is received over the line L2 the operations which take place will be similar to those previously described, except that the key K1 will be placed in its normal middle position in order to connect the operators set to the trunk line; similarly, for an incoming call as received over trunk line L1, the operation will be similar except that the key K1 will be operated to actuate the lower set of springs in order to connect the operators instrument set to'the trunk line L1.

The operator by observing the lamp LA3 can ascertain when a connection has been released; it is not necessary, however, for her to restore the operated keys, such as K1, K2 and K3, unless she has been specially instructed to do so, since all incoming calls will be dealt with by the operator, who will then operate the switching key of the wanted subscriber to a position which correbeen extended.

In the case of outgoing calls, the calling subscriber will remove his hand-set from the cradle and observe the condition of his busy lamp, which is similar to the lamp BL. If the leads from his instrument set are connected to a trunk line which is busy, a circuit will be completed from battery, switch hook springs SH, busy lamp BL, lead L1, springs of switching key K1 to the lower outer armature of one of relays A1, A2 or A3 depending upon the position of the switching key, to earth. If the lamp lights, the calling subscriber will note that the trunk line to which he is connected is busy and will thereupon extend connection over the private automatic exchange to the line OAL to ring the bell BE of the operators set. The operator upon hearing the bell ring will press button L and communicate with the calling subscriber. Upon ascertaining that he wishes to be connected to an idle trunk line she will operate the switching key of that subscriber to connect his line through to an idle trunk line. The calling subscriber can then set up a connection through the public exchange by dialling, in the usual manner. If, however, the calling subscriber wishes the operator to set up the connection for him he will inform the operator who will then set up a connection from her instrument set to the line of the wanted party; when the wanted party replies, the operator will offer. the connection to the calling subscriber in the same way as in the case of an incoming call.

If desired, certain of the trunk lines may be definitely allotted to particular subscribers of importance. For example, the trunk line L1 may be 'allotted to the manager and the switching key corresponding to the managers instrument set will then be permanently thrown to connect his instrument set to the trunk line L1, whilst the a switching keys of other subscribers will be thrown only to positions which connect their instrument sets to the trunk lines L2 or L3. An alternative arrangement would be to arrange that when a call is extended toor'from the managers instrument set all other connections on that trunk line will be disconnected by throwing the corresponding switching keys to anotherposition, in this way the communication between the manager and the subscriber at the public exchange will be private and no other subscriber will be able to hear the conversation.

At night time the alarm key LK will be thrown and when any of the drop indicators are released, a circuit will be completed over the flap of the operated indicator to operate an alarm AL to attract the attention of the attendant. Alternatively,,the keys NKl, NK2 and NK3 may be thrown so that ringing current transmitted from the public exchange is extended to the night bellNB.

In order to provide aconvenient mounting for the busy lamp on a subscribers set, a lamp cap is mounted in the cover of the set whilst the lamp jack is mounted onthe base of the set in such a position so that when the set is assembled the lamp cap is located immediately above the lamp.

What I claim as new and desire to secure by LettersPatent is:

1. In a, telephone system, a private branch exchange having a plurality of local lines, a manual switchboard, a plurality of keys at said switchboard, one for each local line, and a plurality of trunk lines extending from a main exchange and multipled to, each of said keys whereby any local line may be connected to any trunk line by the key associated with the local line.

2. In a telephone system, a private branch exchange having a plurality of local lines, a manual switchboard, a plurality of keys at said switchboard, one for each local line, each key having three positions, and three trunk lines extending from a main exchange and terminating in said switchboard, each trunk line multipled to a corresponding position of each of said keys, whereby any local line may be connected to any one of said trunk lines by the operation of the key associated with the local line to the position corresponding. to the desired trunk line.

3..In a private branch telephone system, a manual switchboarda plurality of keys at said switchboard, a plurality of local lines extending from subscribers stations and each terminating in a different one of said keys, a plurality of incoming trunk lines terminating in said switchboard and multipled to all of said keys, whereby any local line may be connected to any trunk line ;by the key associated with the local line, a lamp at each subscribers station, and means for lighting the lamp at a subscribers station when the associated line is, connected to a busy trunk line.

f1. In a private branch exchange, a manual switchboard, automatic switching apparatus, a plurality of subscribers stations, a line extending from each station and terminating at said switchboard in an individual trunk key, a plurality of incoming trunk lines terminating at said switchboard and multipled to all of said trunk keys, whereby any local line may be connected to any trunk line by the associated trunk key, a second line extending from each station and terminating in said automatic switching apparatus, and two switching devices at each station .for connecting the station to either of said associated lines as desired.

5. In a private branch exchange, a manual switchboard, a pluralityv of keys at said switchboard, a plurality of local lines each terminating in a different one of said keys, a plurality of incoming trunk lines connected in multiple to each of said keys whereby any local line may be connected to any one of said trunk lines by the key associated with the local line, a drop indicatorindividual to each trunk line, a common indicating device, and a key associatedwith each trunk linefor connecting said common indicating device to the trunk line in place of the individual drop indicator.

6. In a private branch exchange, a manual switchboard, a plurality of local lines and a plurality of incoming trunk lines terminating at said switchboard, a key individual to each local line and arranged to connect the associated line with anyone of said trunk lines, an indicator individual to each trunk line operated when a call is received over the trunk line, a relay in each trunk line operated when the trunk line is busy, and means controlled by each relay for shunting the associated indicator to render it inoperative.

7. In a private branch exchange, a manual switchboard, a plurality of local lines and a plurality of incoming trunk lines terminating at said switchboard, a plurality of keys at said switchboard, each key individual to a local line and arranged to connect the associated line with any one of said trunk lines, an indicator individual to each trunk line operated when a call is received over the trunk line, a busy lamp for each trunk line, arelay in each trunk line operated when the trunk line is in use, and means controlled by each relay for shunting the associated indicator to render it inoperative and for lighting the associated busy lamp.

8. In a private branch exchange, a manual switchboard, a plurality of subscribers stations, a line connecting each station with said switchboard, a plurality of incoming trunks terminating at said switchboard, a plurality of keys at said switchboard, each key individual to a line and arranged to connect the associated line with any one of said trunk lines, a lamp at each subscribers station, a relay in each of said trunk lines operated when the associated trunk line is busy, and means controlled by each relay for lighting the lamps at all stations whose lines are connected to the associated trunk line.

9. In a private branch exchange, a manual switchboard, a plurality of subscribers stations, a line connecting with said switchboard, a plurality of incoming trunk lines terminating at said switchboard, a plurality of keys at said switchboard, each key individual to a line and arranged to connect the associated line with any one of said trunk lines, a lamp at said switchboard for each of said trunk lines, a lamp at each subscribers station, a relay in each trunk line operated when the associated trunk line is busy, and means controlled by each relay for lighting the associated lamp at the switchboard and the lamps at all stations whose lines are connected with the associated trunk line.

RUDOLPH FRANK STEHLIK. 

